Double crystal x-ray spectrometer

ABSTRACT

In an X-ray spectrometer comprising a first crystal, a source of X-rays to project X-rays upon the first crystal, a second crystal disposed to receive X-rays reflected by the first crystal and a detector disposed to receive X-rays reflected by the second crystal, the second crystal is revolved about a definite point equally spaced from the first and second crystals at an angular speed of theta , and the detector is revolved about the second crystal at the angular speed of theta , about the definite point at the angular speed of theta and about the first crystal at the angular speed of theta .

0 Umted States Patent [151 3,639,759 Goshi et al. 1 Feb. I, 1972 [54] DOUBLE CRYSTAL X-RAY [56] References Cited SPECTROMETER OTHER PUBLICATIONS [72] Inventors: Yolchi Goshi; Yoshiro Fukao, both of Williams et al.; Journal Optical Society of America; Vol. l8;

Tokyo, Japan (1929); pp. 473 to 478 [73] Assignee: Tokyo Shibaura Electric Co., Ltd., Primary Examiner james Lawrence Kawasaki-5h, Japan Assistant Examiner-A. L. Birch 22 Filed: J 29 9 9 I Att0rneyFlynn 8L Frishauf [21] Appl. No.: 845,842 [57] ABSTRACT In an X-ray spectrometer comprising a first crystal, a source of [30] F i A li ti n priority m X-rays to project X-rays upon the first crystal, a second crystal disposed to receive X-rays reflected by the first crystal and a Aug. 2, 1968 Japan ..43/54845 d t t di po ed to receive X-rays reflected by the second crystal, the second crystal is revolved about a definite point [52] US. Cl ..250/5l.5 equally spaced from the first and second crystals at an angular [51] G01 23/22 speed of 0, and the detector is revolved about the second 58 Field of Search ..250/5 1.5 crystal at the angular Speed of 6, about the definite Point at the X-RAY -X SOURCE angular speed of 0 and about the first crystal at the angular speed of 0.

4 Claims, 3 Drawing Figures PAIENIEum H972 sum 1 or a -x DETECTOR/D SHEET 3 OF 3 PATENTEU FEB 1 i972 DOUBLE CRYSTAL X-RAY SPECTROMETER BACKGROUND OF THE INVENTION This invention relates to the so-called two-crystal X-ray spectrometers utilizing two crystals.

In order to provide X-ray spectrometers of high resolutions the so-called two-crystal X-ray spectrometers have been used wherein the relative angles of two crystals are varied according to the Braggs reflection law. Spectrometers of this type are classified into two types. According to one type the source of X-rays is held stationary, a first crystal is securely mounted on a first rotary shaft which is rotated at an angular speed of and a second crystal is securely mounted on a second rotary shaft which is rotated about its axis at an angular speed of 0 and revolved about the axis of the first shaft at an angular speed of 26. Further, an X-ray detector is disposed to revolve about the axis of the second shaft at an angular speed of 26. In the other type, the first shaft carrying the first crystal and the second shaft carrying the second crystal are mounted on a fixed base, the source of X-rays is rotated about the axis of the first shaft at the angular speed of 20, the first and the second shafts at angular speeds of 0 and 0, respectively, and the X- ray detector is revolved about the axis of the second shaft at an angular speed of-ZB.

The former type requires complicated driving mechanism for these members because of their complicated relations of rotation so that it is difficult to attain high accuracies. Whereas, in the latter type, as it is necessary to rotate the heavy and bulky source of X-rays, it is necessary to use a large driving mechanism. In addition, it is necessary to maintain under vacuum the X-ray passage between the source of X-rays and the first crystal. Further, in both types, the first and second shafts as well as their driving mechanisms should be of high accuracies.

It is, therefore, an object of this invention to provide a novel X-ray spectrometer capable of maintaining respective crystals at a precise angular relationship, thus providing high resolutions with a reduced number of highly precise rotary mechanisms and thus having more simple construction when compared with the prior apparatus.

SUMMARY OF THE INVENTION The spectrometer embodying this invention comprises a first crystal and a second crystal relatively revolvable about the same axis, a detector revolvable with respect to the second crystal, a source of X-rays to project X-rays upon the first crystal, and means to revolve said elements according to the Braggs law.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings FIG. 1 is a schematic drawing to explain the principle of this invention;

FIG. 2 shows a section of one example of an X-ray spectrometer embodying this invention; and

FIG. 3 is a plan view of essential elements of the spectrometer shown in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT First, the principle of this invention will be considered with reference to FIG. 1. A first and a second crystal Q, and Q are positioned at points q, and (1 respectively, on a circle around a point P. These crystals are disposed such that their opposing reflective surfaces are aligned with straight lines respectively interconnecting these crystals and the center P. Near the first crystal is disposed a source of X-rays .r for projecting X-rays upon the reflective surface of this crystal, and a detector D is disposed near the second crystal to receive X-rays reflected by the reflective surface thereof. Thus, X-rays emitted from the source are reflected by the reflective surface of the first crystal toward the second crystal where they are again reflected toward the detector. It is to be understood that first and second crystals Q and 0 are rotated along the circle about the center P and that the first crystal 0, and the detector D are rotated about points q, and 4,, respectively, so as to always cause relative positions between the first crystal 0, and the source of X-rays x and between the second crystal Q and the detector D to satisfy the radiological condition or Braggs condition and to cause the relative angular relationship between the first and second crystals to satisfy said condition.

One embodiment of this invention will now be described with reference to FIGS. 2 and 3, in which elements corresponding to those shown in FIG. 1' are designated by the same reference characters. As shown in FIG. 2. the source of X-rays .r is mounted on a supporting pedestal secured to one end of a baseplate 10. A Soller slit II is secured to the X-ray output side of the source to oppose the first crystal Q which is held by a holder in a conventional manner. The holder is mounted on the upper end of a main shaft 13 through a supporting platform 12. The main shaft 13 is rotatably mounted on the baseplate 10 through a thrust bearing 14. A stationary gear 15 coaxial with the main shaft 13 is secured to the baseplate 10. A gear support 16 is secured to a large diameter portion of the main shaft 13. A thrust sleeve 17 parallel with the main shaft 13 is secured near the periphery of the gear support 16 to rotatably receive a rotary shaft 18. A second gear 19 is secured to the projecting upper end of shaft 18 to rotate therewith. Further, the sleeve 17 carries a third gear 20 which has the same diameter as the second gear 19and is free to rotate with respect to the sleeve 17 and a fourth gear 21 secured to the sleeve. A supporting member 22 is secured to the peripheral portion of the second gear 19 to support the second crystal Q To the periphery of the third gear 20 is secured a supporting plate 23 having a vertical perforation adapted to rotatably receive a shaft 24. The upper end of the shaft 24 supports the detector D via a supporting arm 25 while the lower end is secured to a gear support 26 to rotate therewith. The gear support 26 carries a fifth gear 27 meshing with the fourth gear 21.

The first, second and third gears 15, I9 and 20 mesh with worm gears 28, 29 and 30 respectively, as shown in FIG. 3. These worm gears 28, 29 and 30 are carried by the gear support 16 and are driven in synchronism by a common source of drive through a suitable gear trains. Alternatively, worm gears 28 and 30 adapted to drive the first and third gears 15 and 20, respectively, and the remaining worm gear 29 may be driven by discrete sources of drive, in which case the first and third gears 15 and 20 and the second gear 19 are interlocked through an electric servomechanism. 5

Various elements .r, 0,, 18, Q and D are arranged as diagrammatically shown in FIG. 3. More particularly, these elements are arranged such that the reflective surface of the first crystal Q contains a straight line interconnecting the source of X-rays x and the center q of the main shaft 13 and that upon rotation thereof the center P of shaft 17 will lie on the extension of said straight line. The first and second crystals Q and 0 are symmetrically disposed with respect to the center P with the straight line contained in thin-reflective surfaces. The shaft 24 is located just beneath the second crystal 0 whose center is defined by :1 the axis of shaft 24 being coaxial with the axis of the shaft supporting the second crystal Q The detector D is disposed on the extension of said straight line.

As shown in FIG. 2, the above described elements supported by the baseplate 10 are contained in an evacuated casing 30.

In operation, when the worm gear 28 meshing with the stationary gear 15 is driven, the gear support 16 carrying the worm gear 28 rotates in the direction of an arrow 0 with respect to the source of X-rays and at an angular speed of 0, the main shaft 13 will be rotated with the gear support 16 to rotate the first crystal 0, in the same direction. Concurrently therewith, shaft I8 will be revolved about the axis of main shaft 13 or point 1; at the angular speed of 0 in the direction of arrow b thus revolving the second crystal 0,, and detector D, respectively about point q at the angular speed of 0 and in the directions represented by arrows c and d respectively. At the same time, worm gears 29, 30 and 28 are driven in synchronism to rotate the second and third gears 19 and 20 in the direction of arrow f and at the angular speed of 20. respectively. As a consequence, the second crystal O is revolved about center q, of the first crystal in the direction of arrow and at the angular speed of 0. The second crystal is also revolved about shaft 18 or point P in the direction of arrow f and at the angular speed of 29 thus varying its angle relative to the first crystal Q while satisfying the radiological requirement "or the Braggs condition. Similar to the second crystal 0;, another shaft 24 is revolved about point q in the direction of arrow 0 and at the angular speed 0 and in the direction off and at the angular speed of 20. In addition, shaft 24 is rotated about its own axis at the speed of 6 by the planetary motion of the fifth gear 27 meshing with the fourth gear 21. Thus, the detector D which is integral with shaft 24 is revolved about point q, in the direction of arrow d and at the angular speed of 0 and about point P in the direction of arrow g and at the angular speed of 20. Further, the detector D is revolved about the axis of shaft 24 or point in the direction of h and at the angular speed of 0 thus varying the relative angle with respect to the second crystal while satisfying the radiological requirements.

In this manner, by driving worm gears 27, 28 and 29 by a suitable source of drive (not shown) to rotate the gear support 16 at the angular speed 6 and the second and third gears 19 and 20 respectively at the angular speed of 26, it is possible to vary the relative positions of the source of X-rays x, the first and second crystals Q and Q and the detector D along bent dot and dash lines shown in FIG. 3 while satisfying the radiological requirements.

ln this manner, the adjustment of the relative angle between the first and second crystals Q and Q which essentially requires high accuracy is provided by the rotation of only the gear 19 while other auxiliary motions are provided by other driving means independent of the gear 19. Thus only the shaft 18 and the gear 19 are required to be of high accuracy.

Since independent gears 19 and 20 are provided for shaft 18 and since torques are independently applied for the independent gears 19 and 20, there is no mutual interference between them thus providing more smooth and accurate movement.

Further, as it is not necessary to move the source of X-rays, the construction of the apparatus as a whole is simple, and, in addition, it is very easy to evacuate the passageway of X-rays.

Thus, this invention provides novel two-crystal X-ray spectrometers of simple construction yet having high resolutions and capable of variously varying relative angular relationships between the crystals and the detector at extremely high accuracies and can reduce the number of rotating component parts requiring high accuracies.

What we claim is:

1. An X-ray spectrometer comprising a first crystal, means for rotating said first crystal at an angular speed 6; a source of X-rays for projecting X-rays upon said first crystal; a second crystal disposed to receive the X-rays reflected by said first crystal; means for rotating said second crystal about a definite point at an angular speed of 20, said definite point revolving with said first crystal at the angular speed of 0 and being equally spaced from said first and second crystals; a detector disposed to detect the X-rays reflected by said second crystal; and means for rotating said detector about said second crystal at the angular speed of 6.

2. An X-ray spectrometer comprising a first shaft holding a first crystal on the upper end thereof; a first stationary gear being coaxial with said first shaft; a gear support carrying a worm gear meshing said first gear to drive said gear support at an angular speed of 0 secured to said first shaft; a second gear holding a second crystal; a second shaft being mounted on the peripheral portion of said gear support in parallel with said first shaft, said second gear coaxially secured to said second shaft to rotate at an angular speed of 26; a third gear coaxially mounted on said second shaft to be independently driven at an angular speed of 20; a fourth gear coaxially mounted on said second shaft; a fifth gear meshing with said ourth gear; a third shaft extending through the peripheral portion of said third gear in parallel with said second shaft, said third shaft being coaxial with the center of said second crystal, said second shaft equally spaced from said first and said third shaft, said third shaft being coaxial with said fifth gear; a detector eccentrically mounted on the upper end of said third shaft; and a source of X-rays to project X-rays upon said first crystal; said source of X-rays, said first and second crystals and said detector being arranged such that the X-rays projected by the source are reflected by said first crystal toward said second crystal where they are again reflected toward said detector.

3. The X-ray spectrometer according to claim 2 wherein a conduit is secured to said source of X-rays to surround an X- ray-projecting opening and wherein other component elements than said source of X-rays are contained in an evacuated casing.

4. The X-ray apparatus according to claim 2 wherein said third gear comprises a spur gear having a projecting member at the peripheral portion thereof; said spur gear having the same diameter as said second gear. 

1. An X-ray spectrometer comprising a first crystal, means for rotating said first crystal at an angular speed theta ; a source of X-rays for projecting X-rays upon said first crystal; a second crystal disposed to receive the X-rays reflected by said first crystal; means for rotating said second crystal about a definite point at an angular speed of 2 theta , said definite point revolving with said first crystal at the angular speed of theta and being equally spaced from said first and second crystals; a detector disposed to detect the X-rays reflected by said second crystal; and means for rotating said detector about said second crystal at the angular speed of theta .
 2. An X-ray spectrometer comprising a first shaft holding a first crystal on the upper end thereof; a first stationary gear being coaxial with said first shaft; a gear support carrying a worm gear meshing said first gear to drive said gear support at an angular speed of theta secured to said first shaft; a second gear holding a second crystal; a second shaft being mounted on the peripheral portion of said gear support in parallel with said first shaft, said second gear coaxially secured to said second shaft to rotate at an angular speed of 2 theta ; a third gear coaxially mounted on said second shaft to be independently driven at an angular speed of 2 theta ; a fourth gear coaxially mounted on said second shaft; a fifth gear meshing with said fourth gear; a third shaft extending through the peripheral portion of said third gear in parallel with said second shaft, said third shaft being coaxial with the center of said second crystal, said second shaft equally spaced from said first and said third shaft, said third shaft being coaxial with said fifth gear; a detector eccentrically mounted on the upper end of said third shaft; and a source of X-rays to project X-rays upon said first crystal; said source of X-rays, said first and second crystals and said detector being arranged such that the X-rays projected by the source are reflected by said first crystal toward said second crystal where they are again reflected toward said detector.
 3. The X-ray spectrometer according to claim 2 wherein a conduit is secured to said source of X-rays to surround an X-ray-projecting opening and wherein other component elements than said source of X-rays are contained in an evacuated casing.
 4. The X-ray apparatus according to claim 2 wherein said third gear comprises a spur gear having a projecting member at the peripheral portion thereof; said spur gear having the same diameter as said second gear. 